Referring to FIG. 18, there is illustrated a conventional electric blower 1 including motor unit 2 having rotation shaft 3; and impeller 4 secured to rotation shaft 3. Disposed along and facing the outer periphery of impeller 4 is air guide 5. Reference numeral 6 is a casing air-tightly adjoined with the outer periphery of motor unit 2, the casing enclosing impeller 4 and air guide 5 and having intake opening 6a at the center thereof. Formed along the circumference of casing 6 is a plurality of first exhaust openings 7. Further, one or more second exhaust openings 9 are formed in bracket 14′ accommodating motor unit 2.
The electric blower configured as described above operates as follows. Impeller 4 mounted on rotation shaft 3 of motor unit 2 rotates at a high speed thereby generating suction air stream. Thus created suction air stream travels into air guide 5 from the outer periphery of impeller 4. Some of the suction air stream entering air guide 5 is discharged through first exhaust openings 7 formed in casing 6, and the rest is exhausted through second exhaust openings 9 in bracket 14′ (see, e.g., Japanese Utility Model Laid-open Publication No. 1986-47964).
It is well known in the art that an air blowing efficiency of electric blower 1 can be improved by releasing some of the suction air stream through the periphery of casing 6, as described above. However, a specific shape and area of first exhaust openings 7 and their positions relative to air guide 5 for further enhancing the efficiency of the electric blower have not been studied in detail.